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Diary, March 2011

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Tuesday, March 1, 2011

Our Inner Ape

Today at 11:44, I bought the book Our Inner Ape by Frans de Waal, ISBN:9781862077959 from bookshop De Slegte for € 9.95.

Wednesday, March 9, 2011

Urban HPV

This morning, I went to get my new bike, a brown Urban HPV with a 7-speed transmission and frame number C01037006. Because I am using this bike for going to work, I can buy it with tax reduction. This bike is going to replace the Kronan Klassik that I bought on Monday, April 4, 2005. I decided to buy a bike with a 7-speed transmission because I expect to bike much more now that Li-Xia lives at a care home on the otherside of the town.

Saturday, March 12, 2011

Topographic Atlas of Twente

Today at 16:56:42, I bought ANWB Topografische atlas Overijssel, ISBN:9789018023652 from bookshop Broekhuis for € 9,90. It contains 111 topographic maps on a scale 1:25,000 each covering an area of 5,5 by 8 Km.

Thursday, March 17, 2011


Last Saturday, I watched the movie Proof (2005). I did find this an interesting movie and bought the DVD second hand, which I watched last Monday again, first only to check if it was okay, and then having to watch it till the end.

It made me think about proving P versus NP. I have been thinking that if you want to proof that P equals NP, you need to provide an algorithm (Turing machine according to the official definition) that solves an NP problem in polynomial time. There are two things that you need to do: Proof that it runs in polynomial time to the size of the input and proof that it is correct.

It seems that in order to proof that an algorithm runs in polynomial time, on needs to identify a polynomial of a certain order. It also seems that the order definines the maximum number of nested 'loops', but that it not true. It is possible to think of an algorithm where the number of nested 'loops' depend on the size of the input, where each deeper loop runs in a smaller power than the surrounding loop.

To proof that an algorithm is correct, one needs to proof that with any given input it calculates the correct answer. The general way to proof that an algorithm is correct is to provide an invariant for each step in the algorithm and to show that the invariants are kept during each step of the algorithm.

There are three types of algorithms solving an NP problem. One type find a solution in case there is a solution. The second type tells for a certain choice in the solution, if there exists a solution or not. And the third type simply answers if there exists a solution at all. In a sense all three types of algorithms are equivalent. Take for example the Exact Cover problem where one has to select a number of binary vectors for a given set of vectors such that for each column there is exactly one vector that has a value true in that column. If one has a polynomial algorithm that finds a solution, when there is one or either not, one also has an algorithm that answers the question whether there is a solution at all. If one has an algorithm that for some vector can tell if it is included in a solution or not, one can use this to find a solution. If this algorithm establishes for some vector that it does not occur in any solution, one can simply remove the vector and apply the algorithm on the remaining set of vectors. If it does occur in some solution, one can select it and apply the algorithm on the reduced set of vectors. If one has an algorithm that can determine if a certain set of vectors has a solution, one can simply use it to determine if a certain vector can be included or not by applying the algorithm to the reduced problem where the vector is either included or not. If for one of the types there exists a polynomial algorithm, than one exists for each type.

Friday, March 18, 2011

Curcumin and vitamin D-3

Today, I came across an article about curcumin and vitamin D-3 in relation with positive effects on Alzheimer's Disease. For a long time I have been giving Li-Xia a supplement with curcumine. I do not know whether it has had any positive effect on her Alzheimer's Disease. But I do know that the amount of alergic reactions and itching has reduced and the last year it also seems that she has less problems with feeling cold. I do not know whether this is the result of curcumine, but it is possible, because it does have an anti-inflammatory effect. Curcumine is also said to have a positive effect on the liver and a relationship between the liver and Alzheimer has been suggested. The article noticed that for some people curcumine could have a negative effect on the absorption of amyloid beta. But vitamin D-3 seems to have a possitive effect on everybody. At least half a year ago, I started to give Li-Xia vitamine D-3. In the past months I have reduced the number of supplements that she gets, because swallowing becomes a bigger and bigger problem. At this moment she only gets curcumin and vitamine D-3.

Wednesday, March 23, 2011

Geometric patterns

Today at 11:07, I bought two math related books from bookshop De Slegte and I got one book for free because of the Boekenweek, the Dutch national book week. I picked the (second hand) book De Erfenis (The Inheritance) by Connie Palmen. The first book I bougth, is Het Wiskundeboek, the Dutch translation of The Math Book, ISBN:9789089980373 by Clifford A. Pickover, which costed € 14.95. The second book is Arabian Geometric Patterns, ISBN:9789057681561, published by The Pepin Press, which I bought for € 17.50. This book contains many Arabic Geometric Patterns. Some time ago, I was contacted by Brian Wichmann who informed me about the Tiling Database he maintains with assistance from Tony Lee. His site also hosts Tony Lee's notebooks. Lee also wrote Islamic Star Patterns. The site Taprats provides computer-generated Islamic star patterns. Many pictures and diagrams of Islamic geometric patterns can be found on Pattern in Islamic art.

Thursday, March 24, 2011

Sitting outside

We have a lot of sunny days. Today, it is the first time that my colleagues went outside during lunch time. Two years ago it was March 31 when they did so, but then they still had to put on their coats.

Thursday, March 30, 2011

Magnolia in the rain

This afternoon, it started to rain for the first time after many days with sunshine. It just started raining when I left from the office. When I arrived at home, the rain had almost stopped. In the garden, I noticed that some flower of Magnolia had opened. I took some pictures where you can see the raindrops on the flower leaves.

Natural Proofs

In the past weeks, mainly while biking around the city, I have been thinking a lot about P versus NP. I am more and more becoming convinced that P is not equal NP. Today, I came across the paper Natural Proofs by Alexander Razborov and Steven Rudich. I had heard about this before, but now I am actually thinking about studying the paper. I am afraid that I have been mainly thinking about natural proofs in the past weeks.

Thursday, April 31, 2011

Pioneer Anomaly Solved By 1970s Computer Graphics

Today, I read Pioneer Anomaly Solved By 1970s Computer Graphics Technique on the Physics arXiv Blog, and decided to submit a story to Slashdot, with a reference to this article. It was accepted by CmdrTaco himself. He did a little editting and added two links.

This months interesting links

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